Ternary Oxides of Pre- and Post-Transition Metals for Photocatalytic Solar-to-Hydrogen Conversion

Green hydrogen produced via photocatalysis is a promising sustainable energy source. However, many of the known water-splitting photoactive semiconductors are costly or of low efficiency due to their high electronegativity which impedes the transfer of electrons from the catalyst to chemisorbed/hydrated protons. To address this issue and expand the list of known water-splitting photocatalysts, we build on previous studies [1,2] which showed via data-intensive screening that inserting pre-transition (s-block) metals in binary metal oxides can lower electronegativity while maintaining appealing light absorption properties. Starting from a family of post-transition (p-block) metal oxides used in optoelectronics, we analyze how adding pre-transition metals in these materials impacts the electronic couplings between their constituents and may improve their photocatalytic properties. Then, we screen 109 of these ternary metal oxides using band gaps and band edges predicted at both the semilocal DFT and DFT+U levels of theory. Pourbaix diagrams are also used to assess the stability of the materials in water. Based on the screening protocol, we identify seven ternary oxides among which two appear to not have been previously proposed as water-splitting photocatalysts.

[1] Xiong et al., Energy Environ. Sci. (2021) 14, 2335-2348

[2] Katz et al., Adv. Energy Mater. (2022) 2201869